The present disclosure relates generally to controlling vehicle fluid flow (e.g., airflow) and, in particular, to control logic for reversibly deployable fluid flow control devices with a specific example being an air dam. As used herein, the term “control logic” refers to the logic in a controller that controls a device based on sensor input. The logic of the controller is applied to the sensor input to produce an output control signal for the controlled device. In this way, a fluid flow control device, such as an air dam is adjustable in response to varying conditions.
As used herein, the term “fluid flow” refers to the motion of fluid around and through parts of a vehicle relative to either the exterior surface of the vehicle or surfaces of elements of the vehicle along which exterior fluid flow can be directed. Fluid includes any type of liquid or gas, and the term fluid flow encompasses airflow. Fluid flow over, under, around, and/or through a vehicle can affect many aspects of vehicle performance including vehicle drag, vehicle lift and down force, and cooling/heat exchange for a vehicle powertrain and air conditioning systems. Reductions in vehicle drag improve fuel economy. As used herein, the term “airflow” refers to the motion of air around and through parts of a vehicle relative to either the exterior surface of the vehicle or surfaces of elements of the vehicle along which exterior airflow can be directed such as surfaces in the engine compartment. The term “drag” refers to the resistance caused by friction in a direction opposite that of the motion of the center of gravity for a moving body in a fluid. The term “lift” as used herein refers to the component of the total force due to fluid flow relative to vehicle acting on the vehicle in a vertically upward direction. The term “downforce” used herein refers to the component of total force due to fluid flow relative to the vehicle acting on a vehicle in a vertically downward direction.
Devices known in the art of vehicle manufacture to control fluid flow relative to a vehicle are generally of a predetermined, non-adjustable geometry, location, orientation and stiffness. Such devices generally do not adapt as driving conditions change, thus the fluid flow relative to the vehicle cannot be adjusted to better suit the changing driving conditions, such as deep snow, slush or rainfall. Additionally, current under-vehicle airflow control devices can reduce ground clearance. For example, vehicle designers are faced with the challenge of controlling the airflow while maintaining sufficient ground clearance over parking ramps, parking blocks, potholes, curbs and the like. There is a need for control logic for fluid flow control devices to provide situational tailoring of drag, lift, and cooling fluid flow for a wide range of driving scenarios and operating conditions to improve fuel economy, while providing sufficient ground clearance.